This application relates to a unique location for an oil return tube to ensure that hot oil will be directed onto a motor protector within a sealed compressor, to stop compressor operation during adverse conditions and prevent failure from overheating. Such adverse conditions include, inadequate supply of refrigerant, evaporator or condenser fan failure, etc.
Sealed compressors are utilized to compress a refrigerant in an air conditioning or other environmental conditioning system. As is known, a compressor is sealed, and compresses a refrigerant. The refrigerant is sent to a downstream heat exchanger, and typically a condenser. From the condenser, the refrigerant travels through a main expansion device, and then to an indoor heat exchanger, typically an evaporator. From the evaporator, the refrigerant returns to the compressor.
In the entire refrigerant cycle, there are many reasons why there could be an operating condition that would cause the compressor to overheat and perhaps fail. As one example, the flow of the refrigerant from the indoor heat exchanger, and into the compressor is typically directed over the electric motor for driving the compressor. This refrigerant cools the electric motor, maintaining it at an acceptable temperature. However, and particularly in the case where there is an inadequate supply of refrigerant, the electric motor can become too hot. The same problem could also damage the pump set of the compressor from the heat and effect efficiency. This is undesirable.
Electric motors are typically provided with a motor protector. The motor protector is operable to shut off the motor if there is a spike or other anomaly in the electric power supply. Further, the motor protector is typically provided with some form of temperature sensitive switch that will move to open, and stop operation of the motor should the temperature reach an undesirably high level.
There have been various attempts to address making the temperature sensitive portion of the motor protector more immediately responsive to the actual condition within the compressor. As an example, it might take a relatively long period of time for the inadequate supply of refrigerant in the compressor housing to result in the temperature of the motor protector reaching the high temperature necessary to trip the switch. It would be desirable to reduce the time between the unfavorable condition first occurring, and the stopping of the electric motor operation.
One solution is disclosed in co-pending U.S. patent application Ser. No. 10/235,212, filed on Sep. 5, 2002, entitled “Oil Utilized as Motor Protector Trip for Scroll Compressor,” and now U.S. Pat. No. 6,848,889. In this application, oil from a compressor pump unit is directed downwardly, and toward the motor protector. The oil is at an elevated temperature. The flow of refrigerant within the compressor chamber will typically pull the oil away from the motor protector. Thus, as long as there is an adequate supply of refrigerant, the oil will not contact the motor protector. However, if there is a loss of charge, or a low refrigerant flow situation, the oil will not be pulled away from the motor protector. In that instance, the oil will contact the motor protector, which will quickly trip to stop operation of the electric motor.
In the above-referenced co-pending application, it was mentioned that it is the lower mass flow of refrigerant that allows the oil to contact the motor protector. In fact, with further evaluation, it appears possible that it is not the mass flow of refrigerant that will cause the motor protector to be tripped, but rather the elevated temperature of the oil when there is a loss of charge or a low refrigerant flow situation. In either case, the present invention and the above-referenced application both provide a very simple and reliable method of addressing an adverse condition.
While this broad invention is a good solution to the problem, other improvements upon this basic idea can be made.